/*
 * Copyright (c) 2011-2014 Pivotal Software, Inc.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.camunda.bpm.extension.reactor.projectreactor.selector;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Represents a URI template. A URI template is a URI-like String that contains variables enclosed by braces
 * (<code>{</code>, <code>}</code>), which can be expanded to produce an actual URI.
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @author Jon Brisbin
 * @see <a href="http://bitworking.org/projects/URI-Templates/">URI Templates</a>
 */
public class UriPathTemplate {

  private static final Pattern FULL_SPLAT_PATTERN = Pattern.compile("[\\*][\\*]");
  private static final String FULL_SPLAT_REPLACEMENT = ".*";

  private static final Pattern NAME_SPLAT_PATTERN = Pattern.compile("\\{([^/]+?)\\}[\\*][\\*]");
  // JDK 6 doesn't support named capture groups
  private static final String NAME_SPLAT_REPLACEMENT = "(?<%NAME%>.*)";
  //private static final String  NAME_SPLAT_REPLACEMENT = "(.*)";

  private static final Pattern NAME_PATTERN = Pattern.compile("\\{([^/]+?)\\}");
  // JDK 6 doesn't support named capture groups
  private static final String NAME_REPLACEMENT = "(?<%NAME%>[^\\/.]*)";
  //private static final String  NAME_REPLACEMENT = "([^\\/.]*)";

  private final List<String> pathVariables = new ArrayList<String>();
  private final HashMap<String, Map<String, Object>> vars = new HashMap<String, Map<String, Object>>();

  private final Pattern uriPattern;

  /**
   * Creates a new {@code UriPathTemplate} from the given {@code uriPattern}.
   *
   * @param uriPattern The pattern to be used by the template
   */
  public UriPathTemplate(String uriPattern) {
    String s = "^" + uriPattern;

    Matcher m = NAME_SPLAT_PATTERN.matcher(s);
    while (m.find()) {
      for (int i = 1; i <= m.groupCount(); i++) {
        String name = m.group(i);
        pathVariables.add(name);
        s = m.replaceFirst(NAME_SPLAT_REPLACEMENT.replaceAll("%NAME%", name));
        m.reset(s);
      }
    }

    m = NAME_PATTERN.matcher(s);
    while (m.find()) {
      for (int i = 1; i <= m.groupCount(); i++) {
        String name = m.group(i);
        pathVariables.add(name);
        s = m.replaceFirst(NAME_REPLACEMENT.replaceAll("%NAME%", name));
        m.reset(s);
      }
    }

    m = FULL_SPLAT_PATTERN.matcher(s);
    while (m.find()) {
      s = m.replaceAll(FULL_SPLAT_REPLACEMENT);
      m.reset(s);
    }

    this.uriPattern = Pattern.compile(s + "$");
  }

  /**
   * Tests the given {@code uri} against this template, returning {@code true} if the
   * uri matches the template, {@code false} otherwise.
   *
   * @param uri The uri to match
   * @return {@code true} if there's a match, {@code false} otherwise
   */
  public boolean matches(String uri) {
    return matcher(uri).matches();
  }

  /**
   * Matches the template against the given {@code uri} returning a map of path parameters
   * extracted from the uri, keyed by the names in the template. If the uri does not match,
   * or there are no path parameters, an empty map is returned.
   *
   * @param uri The uri to match
   * @return the path parameters from the uri. Never {@code null}.
   */
  public Map<String, Object> match(String uri) {
    Map<String, Object> pathParameters = vars.get(uri);
    if (null != pathParameters) {
      return pathParameters;
    }

    pathParameters = new HashMap<String, Object>();
    Matcher m = matcher(uri);
    if (m.matches()) {
      int i = 1;
      for (String name : pathVariables) {
        String val = m.group(i++);
        pathParameters.put(name, val);
      }
    }
    synchronized (vars) {
      vars.put(uri, pathParameters);
    }

    return pathParameters;
  }

  private Matcher matcher(String uri) {
    return uriPattern.matcher(uri);
  }

}
